//
//  SportsIconImageGenerator.swift
//  SportsTime
//
//  Generates a 1024x1024 PNG with randomly scattered sports icons.
//

import SwiftUI
import UIKit

struct SportsIconImageGenerator {

    /// All sports icons used in the animated background
    private static let sportsIcons: [String] = [
        // Sports balls
        "football.fill",
        "basketball.fill",
        "baseball.fill",
        "hockey.puck.fill",
        "soccerball",
        "tennisball.fill",
        "volleyball.fill",
        // Sports figures
        "figure.run",
        "figure.baseball",
        "figure.basketball",
        "figure.hockey",
        "figure.soccer",
        // Venues/events
        "sportscourt.fill",
        "trophy.fill",
        "ticket.fill",
        // Travel/navigation
        "mappin.circle.fill",
        "car.fill",
        "map.fill",
        "flag.checkered"
    ]

    /// Generates a 1024x1024 PNG image with randomly scattered sports icons
    /// - Returns: A UIImage with transparent background containing the icons (exactly 1024x1024 pixels)
    static func generateImage() -> UIImage {
        let size = CGSize(width: 1024, height: 1024)
        let maxIconSize: CGFloat = 150
        let minIconSize: CGFloat = 40
        let minSpacing: CGFloat = 80 // Minimum distance between icon centers

        // Use scale 1.0 to ensure exact pixel dimensions (not retina scaled)
        let format = UIGraphicsImageRendererFormat()
        format.scale = 1.0
        let renderer = UIGraphicsImageRenderer(size: size, format: format)

        // Generate well-distributed positions using Poisson disk sampling
        let positions = generateScatteredPositions(
            in: size,
            minSpacing: minSpacing,
            targetCount: 45
        )

        let image = renderer.image { context in
            // Clear background (transparent)
            UIColor.clear.setFill()
            context.fill(CGRect(origin: .zero, size: size))

            // Shuffle icons to randomize which icon appears where
            let shuffledIcons = sportsIcons.shuffled()

            // Draw icons at scattered positions
            for (index, position) in positions.enumerated() {
                let iconName = shuffledIcons[index % shuffledIcons.count]
                let targetSize = CGFloat.random(in: minIconSize...maxIconSize)
                let rotation = CGFloat.random(in: -30...30) * .pi / 180

                // Create SF Symbol image at a large point size for quality
                let config = UIImage.SymbolConfiguration(pointSize: 100, weight: .regular)
                if let symbolImage = UIImage(systemName: iconName, withConfiguration: config) {
                    // Tint with warm orange
                    let tintedImage = symbolImage.withTintColor(
                        UIColor(Theme.warmOrange),
                        renderingMode: .alwaysOriginal
                    )

                    // Calculate proportional size maintaining aspect ratio
                    let originalSize = tintedImage.size
                    let aspectRatio = originalSize.width / originalSize.height
                    let drawSize: CGSize
                    if aspectRatio > 1 {
                        // Wider than tall - constrain by width
                        drawSize = CGSize(width: targetSize, height: targetSize / aspectRatio)
                    } else {
                        // Taller than wide - constrain by height
                        drawSize = CGSize(width: targetSize * aspectRatio, height: targetSize)
                    }

                    // Save graphics state for rotation
                    context.cgContext.saveGState()

                    // Position at the scattered point
                    context.cgContext.translateBy(x: position.x, y: position.y)
                    context.cgContext.rotate(by: rotation)

                    // Draw the icon centered at origin with correct aspect ratio
                    let drawRect = CGRect(
                        x: -drawSize.width / 2,
                        y: -drawSize.height / 2,
                        width: drawSize.width,
                        height: drawSize.height
                    )
                    tintedImage.draw(in: drawRect)

                    context.cgContext.restoreGState()
                }
            }
        }

        return image
    }

    /// Generates well-distributed points using a grid-based approach with jitter
    /// This ensures icons are scattered across the entire image, not clumped together
    private static func generateScatteredPositions(
        in size: CGSize,
        minSpacing: CGFloat,
        targetCount: Int
    ) -> [CGPoint] {
        var positions: [CGPoint] = []

        // Calculate grid dimensions to achieve roughly targetCount points
        let gridSize = Int(ceil(sqrt(Double(targetCount))))
        let cellWidth = size.width / CGFloat(gridSize)
        let cellHeight = size.height / CGFloat(gridSize)

        // Margin from edges
        let margin: CGFloat = 40

        for row in 0..<gridSize {
            for col in 0..<gridSize {
                // Base position at center of grid cell
                let baseCenterX = (CGFloat(col) + 0.5) * cellWidth
                let baseCenterY = (CGFloat(row) + 0.5) * cellHeight

                // Add random jitter within the cell (up to 40% of cell size)
                let jitterX = CGFloat.random(in: -cellWidth * 0.4...cellWidth * 0.4)
                let jitterY = CGFloat.random(in: -cellHeight * 0.4...cellHeight * 0.4)

                var x = baseCenterX + jitterX
                var y = baseCenterY + jitterY

                // Clamp to stay within margins
                x = max(margin, min(size.width - margin, x))
                y = max(margin, min(size.height - margin, y))

                // Randomly skip some cells for more organic feel (keep ~80%)
                if Double.random(in: 0...1) < 0.85 {
                    positions.append(CGPoint(x: x, y: y))
                }
            }
        }

        // Shuffle to randomize draw order (affects overlap)
        return positions.shuffled()
    }

    /// Generates PNG data from the image
    static func generatePNGData() -> Data? {
        let image = generateImage()
        return image.pngData()
    }
}

// MARK: - SwiftUI View for generating and sharing

struct SportsIconImageGeneratorView: View {
    @State private var generatedImage: UIImage?
    @State private var isGenerating = false
    @State private var showShareSheet = false

    var body: some View {
        VStack(spacing: 16) {
            // Preview of generated image
            if let image = generatedImage {
                Image(uiImage: image)
                    .resizable()
                    .aspectRatio(contentMode: .fit)
                    .frame(maxWidth: 300, maxHeight: 300)
                    .background(
                        // Checkerboard pattern to show transparency
                        CheckerboardPattern()
                    )
                    .clipShape(RoundedRectangle(cornerRadius: 12))
                    .overlay(
                        RoundedRectangle(cornerRadius: 12)
                            .stroke(Color.secondary.opacity(0.3), lineWidth: 1)
                    )
            }

            // Generate button
            Button {
                generateNewImage()
            } label: {
                HStack {
                    if isGenerating {
                        ProgressView()
                            .tint(.white)
                    } else {
                        Image(systemName: "dice.fill")
                    }
                    Text(generatedImage == nil ? "Generate Image" : "Regenerate")
                }
                .frame(maxWidth: .infinity)
                .padding()
                .background(Theme.warmOrange)
                .foregroundStyle(.white)
                .clipShape(RoundedRectangle(cornerRadius: 12))
            }
            .disabled(isGenerating)

            // Share button (only visible when image exists)
            if generatedImage != nil {
                ShareLink(
                    item: Image(uiImage: generatedImage!),
                    preview: SharePreview("Sports Icons", image: Image(uiImage: generatedImage!))
                ) {
                    HStack {
                        Image(systemName: "square.and.arrow.up")
                        Text("Share via AirDrop")
                    }
                    .frame(maxWidth: .infinity)
                    .padding()
                    .background(Color.blue)
                    .foregroundStyle(.white)
                    .clipShape(RoundedRectangle(cornerRadius: 12))
                }
            }
        }
        .padding()
    }

    private func generateNewImage() {
        isGenerating = true

        // Generate on background thread to avoid UI freeze
        Task {
            let image = await Task.detached(priority: .userInitiated) {
                SportsIconImageGenerator.generateImage()
            }.value

            withAnimation {
                generatedImage = image
                isGenerating = false
            }
        }
    }
}

// MARK: - Checkerboard Pattern for transparency preview

private struct CheckerboardPattern: View {
    var body: some View {
        Canvas { context, size in
            let tileSize: CGFloat = 10
            let rows = Int(ceil(size.height / tileSize))
            let cols = Int(ceil(size.width / tileSize))

            for row in 0..<rows {
                for col in 0..<cols {
                    let isLight = (row + col) % 2 == 0
                    let rect = CGRect(
                        x: CGFloat(col) * tileSize,
                        y: CGFloat(row) * tileSize,
                        width: tileSize,
                        height: tileSize
                    )
                    context.fill(
                        Path(rect),
                        with: .color(isLight ? Color.gray.opacity(0.2) : Color.gray.opacity(0.3))
                    )
                }
            }
        }
    }
}

#Preview {
    SportsIconImageGeneratorView()
}